One, the main pests
1. This pest is also known as lala or earth dogs. Both adult crickets and nymphs (immature stages) are harmful to potato crops. They use their mouthparts and large front legs to tear underground stems or roots, causing the above-ground parts of the plant to wilt or die. In some cases, they eat the buds, preventing them from growing and leading to a lack of seedlings. These pests also dig tunnels in the soil, separating the roots from the soil, which increases air exposure and causes water loss, affecting seedling growth and even leading to death. In the fall, they bite into the tubers, creating holes that can lead to rot and decay.
Adult and nymph crickets move vertically in the soil depending on temperature changes. During winter, they burrow 1.2 to 1.6 meters deep to hibernate. In spring, they come up to about 10 cm in the tillage layer. They are active at night and hide underground during the day. In summer, when temperatures rise, they go deeper—around 20 cm. In the fall, they return to the tillage layer to feed. They prefer soils with more organic matter and avoid areas with high salt content.
2. Another pest is called the ground silkworm, which is the larval stage of a beetle. It primarily damages the tender roots, underground stems, and tubers of potatoes. It bites and drills into these parts, cutting them neatly and disrupting the flow of nutrients and moisture, eventually causing the above-ground parts to die. When it attacks the tubers, it reduces their quality or causes them to rot. Adult beetles (scarabs) also fly to the plants and chew on the leaves.
Both adults and larvae of this pest can overwinter in the soil. Adults remain less than 40 cm below the surface, while larvae overwinter deeper, around 90 cm. In spring, they move back up to about 10 cm. They are attracted to organic matter and often live in manure piles. Adults are nocturnal, hiding in the soil during the day. The larvae have three pairs of legs, a plump body, and are milky white, often curling into a horseshoe shape when resting.
3. The golden wireworm, also known as the wireworm, is the larval stage of a click beetle. In spring, the larvae drill into the buds, roots, and underground stems, causing the seedlings to gradually wilt or die. Thicker roots or stems are rarely snapped, but young plants are particularly vulnerable. In the fall, the larvae attack the tubers, creating holes that reduce their quality and may lead to rot.
Both adult and larval wireworms burrow deep into the soil (up to 60 cm) in winter to survive. They create small wormholes while moving. In spring, they return to the tillage layer. When soil temperatures exceed 17°C in summer, they move deeper again. In the fall, they return to the upper soil layer. The newly hatched larvae are white, and as they grow, they become shiny and hard, reaching lengths of 2 to 3 cm.
4. The ground tiger, also known as the cutworm, is a type of nocturnal moth whose large larvae are the most damaging. Adults come in two types: small tigers and yellow tigers. Ground tigers mainly harm potato seedlings by cutting them off near the ground, killing the entire plant. They often drag the severed stems into their burrows. Young larvae may also feed on young leaves, creating nicks and holes. They can also damage underground tubers by making small holes.
Ground tiger larvae are typically yellow-brown, dark brown, or black-brown, measuring 3 to 5 cm long. Small tigers prefer moist, weedy fields with high humidity, while yellow tigers favor drier environments and are sensitive to heat. Their adults are attracted to light and molasses.
Second, control methods
The aforementioned underground pests vary in species but share similar behaviors. All are active underground, so their control methods are generally similar.
1. Deep plowing in autumn helps destroy their overwintering habitat. Freezing can kill many larvae and adults, reducing their population for the next season.
2. Field sanitation is important. Remove weeds, debris, and trash from fields, roadsides, and ditches, and dispose of them away from the field to reduce the number of eggs and larvae.
3. Trapping adult pests can be effective. Use molasses traps, black light lamps, fresh horse dung piles, or grass bundles to attract and kill adults that are phototactic or attracted to sweet substances. This reduces oviposition and limits the number of larvae.
4. Chemical control is another option. Apply poisoned soil or granules during sowing: mix 1% trichlorfon powder (3–4 kg per acre) with 10 kg of fine soil, or use 3% carbofuran granules (1.5–2 kg per acre) and spread them in the furrow. Alternatively, spray the roots of seedlings with pesticides. For irrigation, use a 40% phoxim solution diluted 1500–2000 times and apply 50–100 ml per plant. For small areas, mix the pesticide with fried wheat bran, cornmeal, or other baits and spread them in the field at night.
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